Effects of Si, Ti Fe and Na Additives on Surface Acid Property, Structure, and Catalytic Activity of High-temperature Chlorinated #eta#-Alumina

摘要

Studies were made into changes in Lewis acid property, phase transformation rate, and catlaytic activity in the benzene isopropylation of high-temperature chlorinated #eta#-alumina, after doping, Si, Ti, Fe, and Na in bulk of the alumina. Chemical states of the doped elements were also measured using X-ray photoelectron spectroscopy (XPS). During the course of high-temperature chlorination, Ti and Na were remarkedly condensed on the #eta#-alumina surfaces, attributed to diffusive migration from bulk to surface and enhanced phase transformation of #eta#-alumina #alpha#-alumina via #theta#-phase, while Si retarded the phase transformation because diffusive migration of Si in bulk never occurrede. As for the case of Fe, while condensation effect on surface was great and sublimation as iron trichloride took place, but the phase transformation was retarded. Addition of Si below 2.4 wt% and of Ti below 6.0 wt% into #eta#-alumain enhanced the generation of Lewis acid sites, while that of Fe and Na retarded the site generation. When not more than 1.5 wt% of Si and 6.0 wt% of Ti were added, the catalytic activity to liquid-phase benzene isopropylation with propene, at ambient temperature, was effectively improved, while addition of Fe and Na retarded the activity.